I also disagree with block sets. Let us first get a decent set out (or a few), THEN we can look at themes and such. I know for a fact that some advocated a whole Vset devoted to X-ed cards, which is also block spanning.
Perhaps I wasn't very clear what I meant in my earlier post. I'll try to do a better job this time.
The point was I was trying to get at was that I think in the long run it will be much cleaner if every card within a virtual set is allowed in the same formats. That way we avoid having a virtual set where 5 of the cards are allowed in FOTR, TS, and Movie, 2 of the cards are allowed in TS and Movie, and 3 of the cards are allowed in Movie, etc. In my opinion, it would look unorganized and would get confusing very fast (if every virtual set is like that).
I'd prefer if we organized it where all the cards in virtual set #1 are allowed in FOTR, TS, and Movie (which means Fellowship block cards). Then for virtual set #2, we target TS and Movie (which means Tower Block cards). Then for virtual set #3, just target Movie (which means King block cards).
[BTW, this is the same idea that Star Wars CCG did for their first 3 virtual sets to get things started...]
Since the "theme" for the virtual set #1 is basically "remaking the worst or most underused card of each culture in Fellowship block", virtual sets #2 and #3 could continue that theme for Towers and King.
After all that, since we would then have 3 sets out and would have gotten the hang of the process, we then could talk about true "themed" virtual sets, introducing a new keyword, etc.